fix fs module process.binding hackery

Fix the horrible atrocity introduced in
08471b2. Previously it would evaluate
the code directly through process.binding(), and it now creates a new
Object with the prototype being the real fs module, exported by core.

Ref: nodejs/node#2026

fs.js

@@ -1,11 +1 @@
-// eeeeeevvvvviiiiiiillllll
-// more evil than monkey-patching the native builtin?
-// Not sure.
-
-var mod = require("module")
-var pre = '(function (exports, require, module, __filename, __dirname) { '
-var post = '});'
-var src = pre + process.binding('natives').fs + post
-var vm = require('vm')
-var fn = vm.runInThisContext(src)
-fn(exports, require, module, __filename, __dirname)
+module.exports = Object.create(require('fs'))

graceful-fs.js

@@ -1,5 +1,3 @@
-// Monkey-patching the fs module.
-// It's ugly, but there is simply no other way to do this.
 var fs = module.exports = require('./fs.js')
 
 var assert = require('assert')

test/module-evil-hackery.js

@@ -0,0 +1,10 @@
+var test = require('tap').test
+var realfs = require('fs')
+var fs = require('../')
+
+test('module assignment should not leak', function (t) {
+    t.plan(1)
+
+    fs.abc = 3
+    t.equal(realfs.abc, undefined)
+})